The carcinogenic and mutagenic effects of chloroprene (126998) are reviewed. The historical development of concern over occupational exposure to chloroprene is traced. The lack of data that prevents the development of valid inferences regarding the carcinogenicity of chloroprene is highlighted. The consistency of positive responses for the mutagenicity of chloroprene in several test systems is considered. The adverse effects of chloroprene on the reproductive process of exposed workers is discussed.